Addressing the "the social class attainment gap" in education has become a government priority in England. Despite multiple initiatives, however, little has effectively addressed the underachievement of working-class pupils within the classroom. In order to develop clearer understandings of working-class underachievement at this level, this small research study focused on local social processes by exploring how secondary school teachers identified and addressed underachievement in their classrooms. Our analysis shows how teachers' identifications of underachieving pupils overlapped with, and were informed by, their tacit understanding of pupils' social class position. While many teachers resisted the influence of social class, they used stereotypes to justify their practice and expectations, positioning pupils within educational and occupational hierarchies. This, we conclude, suggests the need for more systematic attention to the micro-social processes that provide the conditions through which working-class underachievement is produced. (Contains 1 note and 2 tables.)